Testing Fuel Pump - Mercury 150 EFI Service Manual

FUEL PUMP

Testing Fuel Pump

Low fuel in tank.
Loose fuel line connection.
Fuel pump fitting loose.
A hole or cut in fuel line.
Fuel Pump anchor screw(s) loose.
Fuel Pump filter cover anchor screw loose.
Fuel pump filter gasket worn out.
Fuel pump gasket(s) worn out.
Fuel vaporizing
An anti-siphon valve.
Air in fuel line.
A dirty or clogged fuel filter.
The fuel pickup in fuel tank is clogged or dirty.
Worn out fuel pump diaphragm.
Worn out check valve(s) in fuel pump.
A leaky check valve gasket.
Pulse hole(s) plugged.
Hole in pulse hose.
Loose pulse hose.
Fuel hose internal diameter too small.
Primer bulb check valve not opening.
Excessive fuel lift required.
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Problem: Air Bubbles in Fuel Line
Fill tank with fuel.
Check and tighten all connectors.
Tighten fitting.
Check condition of all fuel lines and replace
Tighten all screws evenly and securely.
Tighten screws securely.
Replace gasket.
Rebuild fuel pump.
Fuel with high reed vapor pressure (winter grade
fuel) may vaporize (form bubbles) when used in
hot/warm weather. Use fuel with a lower reed va-
por pressure (summer grade fuel)
Problem: Lack of Fuel Pump Pressure
See ''Checking for Restricted Fuel Flow" preced-
ing.
See ''Air Bubbles in Fuel Line", above.
Clean or replace fuel filter.
Clean or replace pickup.
Rebuild fuel pump.
Rebuild fuel pump.
Rebuild fuel pump.
Remove fuel pump and clean out holes.
Replace pulse hose.
Tighten connection(s).
Use 5/16 I.D. fuel hose.
Replace primer bulb.
Fuel lift exceeds 2.5 in. of vacuum (mercury)
90-883728 JULY 2001